The invention relates to a feed roller, a feed roller assembly for intermittently feeding sheets, and a sheet handling system.
A feed roller and a feed roller assembly of the mentioned kind are well known in the art. As listed below some of these provide a preceding glide shoe or a side-mounted distance roller for the feed roller. The prior art feed rollers, however still have significant drawbacks.
In U.S. Pat. No. 5,372,359 a gliding shoe is pressed onto the pad. There is a comparatively high coefficient of friction to the pad. This results in: a higher force to drive; a speed limitation with regard to the throughput; and possibly a squeaking noise during separation.
Prior art rollers with side-mounted distance roller are known as a feed roller having a side-mounted distance roller or a feed roller with a distance roller mounted on each side or a feed roller the axle of which has a distance roller for the chord portion on each side of the feed roller. Side-mounted rollers or members are disclosed in JP3162331 A, JP2132025 A, JP1321225 A, and U.S. Pat. No. 4,437,656.
Disadvantages of side-mounted preceding distance rollers or cam shaped members which are side mounted are as follows. The preceding distance roller fixed and restricted to one or both sides of the feed roller is, in principle, intended to hold a retard pad in an appropriate circular distance to the feed roller's arc portion by the time the nose piece of the feed roller is pulling one or several sheets from the lift plate onto the retard pad. But the side-mounted members or rollers will cause the sheets to rise at their center, which is disadvantageous and may, in the worst case, even cause a paper jam. Consequently the problem arises to improve sheet feeding, in particular reliability thereof, whereas still a friction for feeding a sheet should be as low as possible.
This is where the invention comes in, the object of which is to specify a feed roller, a feed roller assembly, and a sheet handling system which have improved reliability of sheet feeding and lower friction for sheet feeding operation.